A.T. Robertson Commentary Mark 4:15

"And these are they by the way side, where the word is sown; and when they have heard, straightway cometh Satan, and taketh away the word which hath been sown in them." — Mark 4:15 (ASV)

Where the word is sown (οπου σπειρετα ο λογος). Explanatory detail only in Mark.

Satan (Σατανας) where Mt 13:19 has

the evil one (ο πονηρος) and Lu 8:12 the devil (ο διαβολος).

Sown in them (εσπαρμενον εις αυτους). Within them, not just among them, "in his heart" (Matt.).